Apparatus for producing high velocity shock waves and gases



Feb. 2, 1960 F R SCOTT ETAL 2,923,852

APPARATUS FOR PRODUCING HIGH VELOCITY SHOCK WAVES AND GASES Filed Oct.21, 1957 Power Supply INVENTOR. Vernal Josephson Y Frank/in R. Scott WW2,923,852 Patented Feb. 2, 1960 APPARATUS FOR PRODUCING HIGH VELOCITYSHOCK WAVES AND GASES Franklin Robert Scott, San Diego, and VernalJosephson, Palos Verdes Estates, Calif., assignors to the United Statesof America as represented by the United States Atomic Energy CommissionApplication October 21, 1957, Serial No. 691,522

2 Claims. (Cl. 315-59) The present invention relates to apparatus forproducing shock waves or detonations of very short duration and fastrise-time. Such shock waves are useful for producing light flashes forhigh speed photography, or for producing X-rays or neutrons, dependingon the type of gas utilized.

A mass of rarified gas in a container is suddenly ionized to produce ashock wave. The container in which the shock wave is produced is taperedin longitudinal configuration in order that the ionized gas or plasmawill be rapidly accelerated to a very high velocity.

It has been found that when such shock waves are produced withsufiicient energy and a suitable gas is utilized a source of prolificX-rays and/or a source of neu trons is produced. The present inventionprovides a compact and portable shock wave, X-ray or neutron source.

It is, accordingly, a prime objective of the present application toprovide a device for producing high velocity shock waves in a gas.

It is the further objective of the present invention to provide a novelportable X-ray and/or neutron source.

The above and other objectives and advantages of the present inventionwill become apparent from the following description and drawing made apart of this specification.

Referring to the drawing, a tapered gas discharge ves- I sel 23,hereinafter termed a shock tube, made of nonconducting materialsurrounded by an envelope or sheath of conducting material, houses atits small end an electrical switch comprising an electrode 19 and acontactor 21. A second electrode 25 has an annular configuration and issupported at the large end of the tapered section of the dischargevessel.

The vessel is completed by a transparent dome section 11 ofsubstantially hemispherical configuration which is hermetically attachedto the large end of the shock tube.

It is desirable to utilize select gases in a device and to this end agetter container 27 is provided in communicative relationship with theinterior of the vessel to eliminate vestiges of unwanted gases. Atoms ofselect gas are supplied from a source 29 herein termed an emitter andwhich is shown connected to and communicating with the interior of thevessel.

The two electrodes 19 and 25 constituting the ionization electrodes areconnected in series with a source of potential 13 and a spark gap 22.The operation of the switch contactor 21 charges capacitor 13. Triggerelectrode 14 fires the spark gap in a manner well known in the art andimpresses the total potential of the power source across the gaseousmedium between electrodes 19 and 25 in the tapered tube.

The imposition of the ionizing potential in the gas within the taperedtube produces a conical gaseous discharge. The high currents produced inthe discharge tend to localize, or pinch, at the axis of the tube byvirtue Of the self-magnetic field. Since the radius of the dischargevessel is less at the small end than at the large end, the compressedionized zone, or pinch, arrives atthe region in the axis at the small'end of the dischargevessel earlier than at the large end and starts amass motion of the heated plasma into the region not yet pinched. Thisaction continues toward the large end of the tube where the shock waveis then driven into the hemispherical end portion of the device.

The high velocity shocks, and the X-rays and/or neutrons produced in thetapered shock vessel are dependent on the value of the current duringthe discharge period, and it is therefore desirable that the amplitudeof the discharge be as great as possible. To this end the componentshave been arranged to take advantage of a very low inductance coaxialcondenser 13 surrounding the power supply and the shock vessel. Thecapacitor constitutes the power source for energizing the shock wavevessel.

The device is useful as a neutron source by utilizing deuterium gas. Forits use as an X-ray or light source, it has been found desirable toutilize argon gas at about 50 p.

In such a device, the shock wave vessel is subject to gradualdegradation, and it is accordingly desirable that it be replaced. It isprovided at its smaller end with an end flange portion 35 adapted to beseated on and sealed to a mating fixed base flange portion 36. Themating flange surfaces may be fiat or contain annular ridges, orotherwise provided with surfaces well known in the art to produce ahermetical joint. The shock tube flange portion may be clamped to thebase flange portion as, for example, by a twist lock device, clamps,bolts or any other suitable clamping means.

An apparatus in accordance with the foregoing description has producedhigh velocity shocks of the order of about Mach by discharging a 10microfarad condenser charged to 25 kilovolts between the electrodes.

The foregoing has described a preferred portable embodiment of myinvention in which very high velocity shock waves can be produced andwhich are suitable for producing light flashes, X-rays or neutrons, asWell as for laboratory studies of the effects of intense ionization ofselected gases. It is understood however, that other embodiments withinthe spirit of this invention are possible,.and therefore the inventionis not to be considered limited by the embodiment shown, but only by theappended claims taken in view of the prior art.

What is claimed is:

1. A device for producing a high energy ionized gas region comprising anevacuated tapered insulating vessel and a substantially hemisphericalinsulating cap hermetically aflixed to the large end of said vessel, anannular electrode having a diameter equal to and supported in the wallof said vessel at the large end thereof and having a conductive portioninside the vessel, a second electrode supported at the small end of saidvessel, means connected to said vessel for introducing a selected gastherein; a source of high potential having two poles,

means for connecting one pole of said high potential source to theannular electrode and means for connecting the other pole of saidpotential source to said second electrode.

2. The device of claim 1 in which said source of electric potential isan annular electrical condenser in which the inner radius is at leastthe radius of said discharge vessel, and means for supporting at least apart of said vessel within the annular space so provided.

(References on following page) 2,928,852 3 4 References Cited in thefile of this patent FOREIGN PATENTS UNETED STATES PATENTS 1,132,526France Nov. 5, 1956 2,712,081 Fearon et a1. June 28, 1955 OTHERREFERENCES 2,728,877 Fischer Dec. 27, 1955 2,756,345 Replogle et a1.July 24, 1956 5 Physlcal July 1957 P

